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London School of Hygiene & Tropical Medicine Malaria Centre

Malaria research in parasite biology

Population genetic structure of Plasmodium falciparum across a region of diverse endemicity in West Africa.

LSHTM investigators:
Victor Mobegi, Taane Clark & David Conway
External collaborators:
Ambroise Ahouidi (Cheikh Anta Diop University, Senegal); Kovana Marcel Loua (The National Institute of Public Health, Guinea); Alfred Amambua-Ngwa, Judith Satoguina & Davis Nwakanma (Medical Research Council, The Gambia); Dominic Kwiatkowski (Wellcome Trust Sanger Institute, UK).
Funding body:
Medical Research Council, UK.

Malaria parasite population genetic structure varies among areas of differing endemicity, but this has not been systematically studied across Plasmodium falciparum populations in Africa.

Ten polymorphic P. falciparum microsatellite loci were genotyped in 268 infections from eight locations in four West African countries (Republic of Guinea, Guinea Bissau, The Gambia and Senegal), spanning a highly endemic forested region in the south to a low endemic Sahelian region in the north. We assessed proportions of mixed genotype infections, genotypic diversity among isolates, multilocus standardised index of association, and inter-population differentiation. Each location had similar levels of pairwise genotypic diversity among isolates, although there were many more mixed parasite genotype infections in the south. Genetic differentiation between populations was low (most pairwise FST values < 0.03), and an overall test for isolation by distance was not significant. Although proportions of mixed genotype infections varied with endemicity as expected, population genetic structure was similar across the diverse sites. Very substantial reduction in transmission would be needed to cause fragmented or epidemic sub-structure in this region. Genome sequences from one of the Guinean sites are now being analysed to compare signatures of selection with those detected in a less endemic region in The Gambia.